A scanning electron microscope (SEM) irradiates an electron beam which is emitted from an electron gun on a sample to detect a secondary electron generated from a surface of the sample, and processes obtained signals to acquire an image (SEM image) by the irradiation of the electron beam. The SEM image is used for observation and measurement of the sample.
The scanning electron microscope has been widely applied to measurement of semiconductor devices. The measurement technique thereof needs to fit to measurement of various types of pattern edges with miniaturization of the semiconductor devices. As one example, the scanning electron microscope performs two-dimensional size measurement such as contact holes and pattern edges of wirings, in addition to one-dimensional size measurement such as conventional lines and spaces. A high-definition image needs to be acquired over an entire field of view for performing the two-dimensional size measurement with high accuracy.
However, in case that the image is acquired using the electron beam, pattern edge information parallel to a scanning direction of the electron beam leads to be missing. To solve the problem, Patent Literature 1 discloses that a line group approximately perpendicular to a pattern edge and a line group approximately parallel to the pattern edge are created based on shape information of the pattern edge as a detected object. Patent Literature 1 further discloses that a vertical scanning direction of the electron beam is decided with respect to the pattern edge based on a lattice group delimited by these line groups.
Thus, a clear image of the pattern edge can be acquired by making an extending direction of the pattern edge be perpendicular to the scanning direction of the electron beam.